#define _CRT_SECURE_NO_WARNINGS 1

class Solution {
public:
    vector<vector<int>> matrixBlockSum(vector<vector<int>>& mat, int k) {
        int n = mat.size(), m = mat[0].size();
        vector<vector<int>> dp(n + 1, vector<int>(m + 1));
        for (int i = 1; i <= n; ++i)
        {
            for (int j = 1; j <= m; ++j)
            {
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1] + mat[i - 1][j - 1];
            }
        }

        vector<vector<int>> ret(n, vector<int>(m));
        for (int i = 0; i < n; ++i)
        {
            for (int j = 0; j < m; ++j)
            {
                int x1 = max(i - k, 0) + 1;
                int y1 = max(j - k, 0) + 1;
                int x2 = min(i + k, n - 1) + 1;
                int y2 = min(j + k, m - 1) + 1;
                ret[i][j] = dp[x2][y2] - dp[x1 - 1][y2] - dp[x2][y1 - 1] + dp[x1 - 1][y1 - 1];
            }
        }

        return ret;
    }
};